00:00 / 00:00
Contracting the immune response and peripheral tolerance
0 / 6 complete
The adaptive immune system, specifically the T- and B-cells, is the part of the immune system that is immunologically tolerant or unresponsive to self-antigens. Immunological tolerance can develop through two mechanisms- central and peripheral. Central tolerance mechanisms eliminate self-reactive lymphocytes during their initial development in the bone marrow and thymus. Peripheral tolerance mechanisms eliminate self-reactive lymphocytes that escape the radar of central mechanisms; in the peripheral tissues and secondary lymphoid organs. Failure of these mechanisms can result in autoimmune diseases like systemic lupus erythematosus.
Now, the immune response is like a community of cells that fight together. Antigen-presenting cells, like dendritic cells, pick up antigens floating around in the body and serve them to naive T-cells, partially stimulating their activation. When the antigen is foreign, it strongly induces the expression of co-stimulatory proteins like the B7 on the antigen-presenting cell surface. B7 binds to the CD28 receptor on the naive T-cell and provides the additional stimulation needed to completely activate them, and also helps in their differentiation into specific types like effector or memory T-cells.
The CD4+ helper T cells are one of the most important immune cells. They secrete cytokines and provide signals that promote B-cell differentiation into plasma cells, class switching, and antibody production. CD4+ helper T cells also secrete cytokines that recruit phagocytes and help them kill more effectively. That’s why many of the peripheral tolerance mechanisms are aimed at shutting down CD4+ helper T cells.
Peripheral tolerance refers to immunological tolerance developed after autoreactive T and B cells mature and enter the periphery. It enables the immune system to recognize and tolerate self-antigens or non-harmful foreign antigens in the body. Peripheral tolerance involves the suppression of autoreactive cells by 'regulatory' T cells, and the generation of hyporesponsiveness (anergy) in lymphocytes which encounter antigens in the absence of the co-stimulatory signals that accompany inflammation, or in the presence of co-inhibitory signals.
Copyright © 2023 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Cookies are used by this site.
USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.